Helical drum scanner



Ot. 8, 1929. c. F. JNKI'NS y y 1,730,975

HELICAL DRUM SCANNER Fiied June 1s. A1928 Patented Oct. 8, y17929 UNITED STATES PATENT OFFICE CHARLES FRANCIS JENKINS, 0F WASHINGTON', DISTRICT OF COLUMBIA, ASSIGNOR T0 JENKINS LABORATORIES, 0F WASHINGTON, DISTRICT OF COLUMBIA, A. CORPORA- TION 0F THE DISTRICT OF COLUMBIA HELICAL Daum SCANNER Application tiled .Tune 13,

This invention relates to radiovisors, i. e., apparatus foil the reception of motion pictures'bradcast by radio, and has for its principal object simple, inexpensive apparatus of small size, and producing a relatively large picture of superior quality.

Heretofore the generally employed method picture but one inch square. For a picture` two inches square with the same number of lines per picture, requires a disc four feet in diameter, and an enormous increase "in the power of the motor required to drive it at speed, an increase equal to the ninthpower of the increase in speed. Reduced to merchandising terms, this means a device impractical for use in the average home.

A still further limitation of the disc method of scanning is that the whole picture area of the surface scanned is lighted simultaneously, and, therefore, requires a radio power amplitier (many times greater than a method which consists of but a small glow area). This power amplifier required still further limits the acceptability of the apparatus for the average home, for it cannot be attached to the usual two-stage amplifier radio set.

The employment of a drum as the scanning means, as providedin the present invention, is without the limitations cited above, for eX- ample, the picture may be increased, by (l) an increase inthe speed of rotation; and/or 2) an increase in the diameter of the drum; and/or (3) a lesser increase in both.

Among its further advantages, incident to the above, is that the scanning means is very light, with moderate peripheral speed, and, therefore, requires but a small motor.

The scanning apertures. in the drum method, are all equi-distant from each other, and, therefore, distortion due to varying spacingr of apertures in the disc method, is entirely eliminated.

1928. Serial No. 285,015.

Also, with this drum method of scanning, each helical turn of the scanning apertures can be lighted independently by its own particular glowing target, which results in a great economy of-current required for light ing the entire picture.

Withthis and other objects in view, the invention consists ofthe novel combination of elements herein described, illustrated in the drawings, and particularly pointed out in the claims.

In the drawings, Figure l is a top view of the drum; Figure 2 an end view thereof; and Figure 3 a sectional view of the lamp employed therewith.

In theiigures, A is the scanning drum; B'

the scanning apertures therein arranged in a four-turn helix; C the lamp which encloses ythe glowing targets C1, C2, C", and C4.

' Between the lamp and the inner periphery ofthe drum lies a vfunnel structure I), divided by very thin partitions into four parts or sections. The small end of each section of this multiple funnel structure lies over its particu lar glowing light target.

The larger end has an openingin length equal to thecircumferential separation ofthe scanning apertures, and a width equal to the helical separation of the holesv beginning and ending the helical turn.

Therefore, the light from each target is confined to the illuminationrof hut ay single helical turn of the scanning apertures. Again, as the mouth of the funnel is only as wide as the circumferential separation be twee-n any two scanning apertures, the result is that but a single aperture is illuminated at' any one moment. y

As the generally accepted method of scanning in receiving instruments is so well known to those skilled in this art, a description of the o eration in meticulous detail is not believe necessary.

In general, however,the method consists, first, in turning the scanning drum as many times per picture asthere are helical turns of the circumferential line of scanning apertures; second, lighting the glow targets or light sources one at a time in synchronism with each rotation of the drum, for example as disclosed in United States Patent No.. 1,683,137 granted to C. F. Jenkins September 4, 1928; and third, so controlling the light values of the glow targets by the incoming radio signals that a pictureis built up therefrom.

It is obvious that I do not wish to limit myself to the tour-turn helix drum shown, nor to the quadruple target neon lamp illustrated, for it is obvious that these elements may be Varied to suit the particular requirements of the problem in hand.

For example, a larger picture may require more helical turns, but, being a drumstructure, such increase does not introduce any picture distortion.

l. ln an apparatus of the class described the combination of a light source, a hollow ro.I tatable cylinder, means for rotating said cylinder, and a stationary light confining channel extending from the light source to the wall of the cylinder.

2. An apparatus according to claim l in. which the channel is in the Jform of a tunnel having its restricted opening adjacent to the light source.

3. An apparatus according to claim l, in which the channel is in the form of a tapered housing having its enlargedl end of rectangular contour adjacent the wall of the cylinder.

4. An apparatus according to claim l in which the channel is in the form ot a tapered housing and is subdivided into a plurality of funnel shaped compartments each having its constricted end adjacent the light source, and its enlarged end adjacent the wall of the cylinder.

5. in an apparatus of the class described the combination of a light source, a hollow rotatable cylinder, a plurality of stationary light coniining channels between said light source,'and the wall of said cylinder, and means for causing light from said source to pass through each of said channels in succession.

6. ln an apparatus of the class described the combination'of a drum-like structure having apertures inthe periphery thereof of a size corresponding to elemental areas of a visual representation to be reproduced, said apertures being arranged in a plural turn helix, a light source and a stationary light conlining channel between said light source .and the 'drum periphery.

7. An apparatus according to claim 6 in which Vthe light conning channel is subdivided into separate'compartments each corresponding to a turn of said helically arranged perforations.

8. ln an apparatus of the class described the combination of a drum-like structure, a light source on the interior of said drum, said 'drum having pertorations in the wall thereor arranged in a plural turn helix, and a plurality of stationary'light confining paths between said light source and each of the helical turns of perforations.

9. The method of scanning employing a drum having perforations therein in the form of a plural turn helix, which comprises projecting a stationary spot of light on the wall of said drum, said spot having a length corresponding to the distance between successive perforations of a helical turn, and a width corresponding to the spacing between the helical turns.

10. In a television system the method ot scanning employing a drum having perforations in a plural turn heliX, which comprises projecting a stationary spot of light upon the wall ot the drum, rotating said drum, subdividing said spot into smaller spots each corresponding to a helical turn of perforations, and rendering each of said spots successively effective in illuminating the wall of said drum.

l1. ln a television system the combination of a hollow drum, a source of perforation in the wall of said drum arranged in the form of a plural turn helix, a plurality of spacially discreet light targets within said drum, and

a stationary light confining channel between each target and a corresponding helical turn of perforations in the drum.

-ln testimony whereot have aiiixed my signature.

CHARLES FRANCIS JENKlNS. 

